A polycarbonate resin is used for many applications such as mechanical parts, auto parts, electric and electronic parts and office equipment parts as it has excellent properties such as mechanical strength, dimensional stability and flame retardancy. Due to the recent dissemination of mobile information terminals such as smartphones and tablets, mechanical strength, especially impact resistance in various environments is now required as compared with conventional information terminals. Most of exterior materials are coated from the viewpoints of a superior design and a good appearance. Therefore, a good appearance and impact resistance in a coated state are required for resins for mobile information terminal housings, and further improvement is desired than conventional polycarbonate resins.
Patent Document 1 reports a resin composition which comprises an aromatic polycarbonate resin, a polyolefin resin and an acrylic elastic polymer containing acrylic rubber containing 8 to 31 wt % of butadiene as a key component and has improved low-temperature impact resistance. Although the resin composition satisfies the requirement for mechanical strength, it has a big problem with chemical resistance.
Patent Documents 2 and 3 report a resin composition comprising a specific acrylic elastic polymer out of the above components. However, the resin composition is unsatisfactory in terms of flowability and chemical resistance.
Meanwhile, as a resin having excellent low-temperature impact resistance, there is known a polycarbonate-polydiorganosiloxane copolymer resin (for example, Patent Document 4). Further, Patent Document 5 reports a resin in which polysiloxane domains having an average domain size of 20 to 45 nm are incorporated into a polycarbonate matrix. This report teaches that when the polysiloxane domains have a specific size, low-temperature impact resistance becomes high. However, these polycarbonate-polydiorganosiloxane copolymer resins may produce a coating defect and are unsatisfactory in terms of impact resistance after coating.
Patent Document 6 reports a resin composition obtained by mixing a rubber-like elastic material with a polycarbonate-polydiorganosiloxane copolymer resin as a resin composition having excellent impact resistance. This resin composition may produce a coating defect, and there is no description of impact resistance after coating.
As a resin composition comprising a polycarbonate and having both impact resistance and organic solvent resistance, Patent Document 7 reports a resin composition which comprises an aromatic polycarbonate, a polycarbonate-polydiorganosiloxane copolymer resin and a hydrogenated aliphatic diene-vinyl aromatic block copolymer graft modified by an unsaturated dicarboxylic acid. However, this resin composition may produce a coating defect and needs to be further improved.
Patent Document 8 reports a resin composition which comprises an aromatic polycarbonate resin, a polyolefin resin and an acrylic elastic polymer. This report states the improvement of low-temperature impact resistance and chemical resistance. However, the resin composition is unsatisfactory in terms of the properties of a thin molded article thereof close to a housing for actual mobile information terminals.
Patent Document 9 discloses a mobile electronic equipment housing which comprises a polycarbonate-polydiorganosiloxane copolymer resin having a specific siloxane chain length and an aromatic polycarbonate except for the copolymer resin. However, this resin composition may produce a coating defect and needs the further improvement of chemical resistance.
Meanwhile, Bledzki et al. report that impact resistance at −20° C. is improved by adding 3 wt % of polypropylene to a polycarbonate resin in non-Patent Document 1. However, this resin composition is also still unsatisfactory in terms of low-temperature impact resistance and has a problem that a molded article thereof has a poor appearance. Therefore, it is not suitable for use in actual molded articles.
Patent Document 10 discloses that a molded article produced by adding a low-density ethylene-based copolymer to a polycarbonate resin has improved chemical resistance while it retains impact resistance. However, this document is silent about low-temperature impact resistance. The resin composition disclosed by this document is unsatisfactory in terms of the properties of a thin molded article thereof close to a housing for actual mobile information terminals.    (Patent Document 1) JP-A 58-34850    (Patent Document 2) JP-A 56-76449    (Patent Document 3) JP-A 4-249576    (Patent Document 4) JP-A 5-247195    (Patent Document 5) JP-B 2006-523243    (Patent Document 6) JP-A 4-225060    (Patent Document 7) JP-A 3-229755    (Patent Document 8) JP-A 2010-222480    (Patent Document 9) JP-A 2011-21127    (Patent Document 10) JP-A 2010-261009    (Non-Patent Document 1) ANTEC2001 p. 1737-p. 1740